1. Field of the Invention
The present invention relates to an etching method, and more particularly to a dry etching method for use in the manufacture of a semiconductor integrated circuit.
2. Description of the Prior Art
For the manufacture of semiconductor integrated circuits, a dry etching process is now attracting attention for the reason that it permits fine etching of a substrate, as compared with a wet etching technique.
According to conventional dry etching methods, a substrate to be etched is disposed in an etching chamber, in which a reactive gas is excited through use of DC energy, high-frequency wave energy or microwave energy for etching the substrate.
With the method employing the microwave energy, the reactive gas can be formed as an excited reactive gas of no great kinetic energy. Accordingly, this method is superior to the other methods in that it is capable of etching the substrate without impairing it by sputtering.
It has also been proposed, as another dry etching process, to excite the reactive gas by light energy in the etching chamber in which the substrate to be etched is placed.
This method also possesses the advantage of etching the substrate without causing any damage thereto by sputtering, for the same reason as is the case with the method utilizing microwave energy.
However, the method utilizing microwave energy and the method utilizing light energy are both far lower in the etching rate than the etching methods using DC energy and high-frequency wave energy, and hence consume a far longer period of time for etching than do the latter methods. Futhermore, the method utilizing the microwave energy encounters difficulty in forming the excited reactive gas over a wide region, and hence is defective in that it is difficult to etch a substrate of a large area uniformly all over it at a time. In the case of the etching method utilizing light energy, some of reactive gases that can be used with the etching method employing microwave energy cannot be sufficiently excited by light energy. Therefore, this method has the shortcoming that it cannot be used with relatively easily available reactive gases.